UNSTEADY FACTORS AFFECTING SALT DIFFUSION IN THE STRATIFIED FLOW SYSTEM AT A RIVER MOUTH

影响河口层流系统盐分扩散的不稳定因素

基本信息

批准号：
04452231
负责人：
YOSHIDA Shizuo
金额：
$ 3.26万
依托单位：
Hokkaido University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1992
资助国家：
日本
起止时间：
1992 至 1994
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-04452231/
关键词：
River Mouth Stratified Flow Two-Layr Flow Salt Diffusion Salt Wedge Entrainment Coefficient Interfacial Instability 界面不安定多層流界面波

项目摘要

The problem of salt diffusion in highly stratified flows such as those found at the mouth of a river is vital to considerations of agriculture and fisheries. Placement and control of the gates governing extraction of fresh water from a river have become social issues. Previous research has assumed that these flows are steady, and has focussed on problems of shear instability in the vicinity of the interface and natural turbulence. The research described below has examined these flows from the practical standpoint of whether and to what extent unsteady factors such as atmospheric pressure, tide, river flowrate, and wind affect salt diffusion around the river mouth. Those results have been used to attempt to develop an expression for improving predictions of the salinity of the river surface at any given point and time.These studies have been carried out mainly in the lower basin of the Ishikari River, Hokkaido, which is typical of a highly stratified flow. Observations were carried out … More in the summers of 1992,1993 and 1994 for about two months each. The observation methods were improved year by year and enough qualitative and quantitative data have been taken to fulfilll the research goals described above. The results of our research are as follows :1) Wind is the dominant factor in the surface salinity of a river. 2) The average entrainment coefficient of the salt wedge is given by the following formula : E = 1.92 * 10^<-6>e^<0.405^^W> for 118m^3/sec, E =2.24*10^<-6>e^<0.281^^W> for 146m^3/sec 3) The process of diffusion of salt from the salt wedge to the surface of a river has been shown to be the following : Wind blows>waves are generated>the turbulence in the upper layr increases>the distribution of salt in the upper layr is rendered uniform>the density gradient around the interface increases>the salt diffusion across the interface increases>the surface salinity increases. 4) The time average profiles of the flow system are stable throughout almost the entirity of the stratified flow system. 5) The process of diffusion is accelerated by an increase in river flowrate, but the salinity of the river water flow itself decreases. 6) Bridge piers and protuberences in the river bottom cause great disruptions in the interface, but the effect of these disruptions on salt diffusion is localized. 7) In order to predict the present surface salinity at any location it is sufficient to have an hourly record of wind speed along the river course and the discharge rate. Less

在高度分层的流中（例如在河口发现的水）中盐扩散的问题对于考虑农业和渔业的考虑至关重要。对从河流中提取淡水提取的门的放置和控制已成为社会问题。先前的研究假设这些流量是稳定的，并且集中在界面附近的剪切不稳定性问题和自然湍流中。下面描述的研究从实际的角度研究了这些流，即是否以及在何种程度上不稳定的因素，例如大气压力，潮汐，河流流量和风影响河流周围的盐扩散。这些结果已被用来开发一种表达式，以改善在任何给定点和时间的河流表面盐度的预测。这些研究主要是在北海道的Ishikari河的下盆地进行的，该河通常是高度分层的。进行了观察，在1992年，1993年和1994年的夏季进行了大约两个月。观察方法逐年改进，并采用了足够的定性和定量数据来实现上述研究目标。我们的研究结果如下：1）风是河流表面盐楔的主要因素。 2) The average entrancement coefficient of the salt wedge is given by the following formula : E = 1.92 * 10^<-6>e^<0.405^^W> for 118m^3/sec, E =2.24*10^<-6>e^<0.281^^W> for 146m^3/sec 3) The process of diffusion of salt from the salt wedge to the surface of a river has been shown to be the following: Wind打击>生成波>上层上升的湍流>上层盐中盐的分布均匀>界面周围的密度梯度增加>跨界面上的盐扩散增加>表面盐度增加。 4）流动系统的时间平均值在几乎整个分层流系统中都是稳定的。 5）扩散过程通过河流流量的增加加速，但河水流的盐度本身降低。 6）河底的桥墩和底座在界面造成了极大的破坏，但是这些破坏对盐扩散的影响是局部的。 7）为了预测在任何位置的当前表面盐度，就足以在河道沿河道和排放速度的风速记录时足够。较少的